Effect of enzymatic versus titanium dioxide/silicon dioxide catalyst on crystal structure of ‘green’ poly[(butylene succinate)‐co‐(dilinoleic succinate)] copolymers

Abstract

AbstractFocusing on an eco‐friendly approach, biodegradable poly[(butylene succinate)‐co‐(dilinoleic succinate)] (PBS‐DLS) copolymers with 70:30 (wt%) ratio of hard to soft segments were successfully synthesized via various processes and catalytic systems. In this approach, biobased succinate was polymerized with renewable 1,4‐butanediol and dimer linoleic diol to obtain ‘green’ copolyesters as sustainable alternatives to petroleum‐based materials. In the first procedure, a two‐step synthesis in diphenyl ether was performed using Candida antarctica lipase B (CAL‐B) as a biocatalyst. A second material was produced via two‐step melt polycondensation in the presence of heterogeneous titanium dioxide/silicone dioxide (C‐94) catalyst. The obtained PBS‐DLS copolyesters were further characterized in regard to their number‐average molecular weight (Mn), chemical structure, thermal transition temperatures and crystallization behavior. Here, digital holographic microscopy was used to study the crystallization behavior of synthesized segmented copolyesters for the first time. Using this technique, it was possible to reveal the twisting of crystalline regions in formed spherulites and observe the differences in crystallization behavior of copolyesters depending on the type of catalyst used in their synthesis. Structural characterization indicated random and blocky structure of copolymers depending on the type of catalyst. Mn was noticeably higher in the case of PBS‐DLS 70:30 copolymer catalyzed using C‐94 than PBS‐DLS 70:30 synthesized with the use of CAL‐B. However, the degree of crystallinity was lower for polymer catalyzed with the heterogeneous catalyst. Furthermore, differential scanning calorimetric thermal analysis revealed that synthesized copolyesters exhibit low glass transition temperature as well as high melting point which are typical for thermoplastic elastomers. © 2020 Society of Chemical Industry